BEIRUT - At least 19 civilians, including five children, were killed by a Syrian regime barrel bomb attack and rebel rocket fire in Aleppo, a monitoring group said on Thursday.

Fifteen of the civilians, among them four of the children and a pregnant woman, were killed in a barrel bomb strike on Wednesday evening on a rebel-held district of the divided northern city, the Syrian Observatory for Human Rights said.

"The children were aged under 10," said Observatory chief Rami Abdel Rahman.

The crude explosives-filled container hit a building in the northeastern neighbourhood of Karam al-Beik as residents were sitting down to break the daytime fast observed during the Muslim holy month of Ramadan.

An AFP journalist saw men screaming as they carried the lifeless body of a boy out of the partly collapsed building before covering him with a makeshift shroud.

Another group brought a dazed elderly man out of the rubble.

The rescue teams, wearing hard hats with headlamps attached, struggled to pick through the rubble in the darkness, some using picks or just their hands to search for survivors.

The other four civilians were killed by rebel rocket fire on the government-held district of Midan later on Wednesday evening, the Observatory said.

Twenty people were also wounded, the Britain-based group said.

For the past three years, Syria's pre-war economic hub has been divided between a government-held western sector and a rebel-held eastern one.

The rebels launched a major offensive in the first week of July to try to take territory on the western outskirts of the city.

More than 220,000 people have been killed in Syria since the conflict began with anti-government protests in March 2011 that were met with a bloody crackdown.